November 04, 2010

Brains to Hand-axes

Stone Age humans were only able to develop relatively advanced tools after their brains evolved a greater capacity for complex thought, according to a new study that investigates why it took early humans almost two million years to move from razor-sharp stones to a hand-held stone axe.

Methodology/Principal FindingsHere we employ a data glove to record manual joint angles in a modern experimental toolmaker (the 4th author) replicating ancient tool forms in order to characterize and compare the manipulative complexity of two major Lower Paleolithic technologies (Oldowan and Acheulean). To this end we used a principled and general measure of behavioral complexity based on the statistics of joint movements.

Conclusions/SignificanceThis allowed us to confirm that previously observed differences in brain activation associated with Oldowan versus Acheulean technologies reflect higher-level behavior organization rather than lower-level differences in manipulative complexity. This conclusion is consistent with a scenario in which the earliest stages of human technological evolution depended on novel perceptual-motor capacities (such as the control of joint stiffness) whereas later developments increasingly relied on enhanced mechanisms for cognitive control. This further suggests possible links between toolmaking and language evolution.

1 comment:

"This further suggests possible links between toolmaking and language evolution."

Interestingly, the most compelling examples of parallels to human language and speech among primates come not from the big apes but from New World monkeys (Platyrrhines). There the evolution of language is related not to tool use but to the fact that, unlike Old World monkeys, New World monkeys are exclusively arboreal and hence they rely not so much on visual as on auditory clues. See Snowdon in "New world primates: ecology, evolution, and behavior."

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